What you need: Thrift store picture frames with glass. The glass is key! If you can find some that are chipped or cracked even better, that will add to the vintage feel. You will also need a spray bottle with one part vinegar to 3 parts water. And lastly you will need the miracle product KRYLON LOOKING GLASS SPRAY PAINT.
Barn Window to Antique Mirror with Looking Glass Spray Paint
Get the Mercury Glass look by pre-spraying your desired object with water and just a touch of dish liquid, spray with Krylon Looking Glass paint, let dry, repeat process until you achieve the 'depth' you are happy with.
33 Ways Spray Paint Can Make Your Stuff Look More Expensive